Predator 212 performance issues

[Harquebus]

This calculator is a good one as any (even though it says “go kart”), has “sliders” so you don’t have to keep typing in the input variables plus has the jackshaft option. The tach is crucial--you have to know the rippems (RPM) to utilize it correctly.

https://www.gokartguide.com/gear-ratio-chart-speed-calculator/

 

[Papapoo]

This calculator is a good one as any (even though it says “go kart”), has “sliders” so you don’t have to keep typing in the input variables plus has the jackshaft option. The tach is crucial--you have to know the rippems (RPM) to utilize it correctly.

https://www.gokartguide.com/gear-ratio-chart-speed-calculator/

Thank you, I will let all of you know when I get the tach.

 

[ole4]

nice bike and love the foxbody!

 

[Papapoo]

nice bike and love the foxbody!

Thank you man, that’s my dad’s car. If you want I can put a link to the forums where he posts about it; https://stangnet.com/mustang-forums...tchback-restoration-performance-build.911535/

 

[Papapoo]

Tach is arriving Sunday. I’ll let you all know the results then.

 

[Papapoo]

Just tested the bike with the tachometer. 2500 RPM and a top speed of 41.26 MPH. Something is DEFINITELY wrong. The bike also started bogging out when I fully opened her up. I believe the carb is at fault here. I had the bike up on a bucket and let it rev out, it revved to 3900 RPM. I have zero clue what’s wrong. Any advice?

 

[Havasu Dave]

sigh.

 

[Papapoo]

sigh.

Tell me about it.

 

[Havasu Dave]

Tell me about it.

Several members have told you your ratio is too tall. You don't have the power to pull it and you never will. Fix your gearing, then worry about your tuning.

 

[sparkwizard]

At 45 MPH, you should be around 4500 RPM. Put those numbers in your calculator, since you do not seem to believe us.

 

[Havasu Dave]

FYI- you will find that once you get the final ratio to something the engine likes, you will gain a bit on the top end, and a whole bunch on accelleration- and for me, accelleration is where the fun is, not top speed.

 

[Mark Brooks]

FYI- you will find that once you get the final ratio to something the engine likes, you will gain a bit on the top end, and a whole bunch on accelleration- and for me, accelleration is where the fun is, not top speed.

Yeeeeah what he said ^^^^^

 

[JimN]

Just tested the bike with the tachometer. 2500 RPM and a top speed of 41.26 MPH. Something is DEFINITELY wrong. The bike also started bogging out when I fully opened her up. I believe the carb is at fault here. I had the bike up on a bucket and let it rev out, it revved to 3900 RPM. I have zero clue what’s wrong. Any advice?

The first thing I would do is verify your tach is on the right setting, cause 2500 rpm at 41 mph with 12" tires and 4:1 ratio is messed up.
I assume you're using an app on your phone to get mph. I'd verify that too.

 

[sparkwizard]

Tach should be in 2 cycle mode. Magneto fires on every revolution. Good point, @JimN

 

[creia]

Tach should be in 2 cycle mode. Magneto fires on every revolution. Good point, @JimN

Why is that? The engine is a (4 cycle) HF 212 Predator.
Michael

 

[sparkwizard]

.

 

[sparkwizard]

Why is that? The engine is a (4 cycle) HF 212 Predator.
Michael

The ignition fires every time the magnet passes the coil. The ignition runs off the crankshaft, not off the camsheft, like a distributor in a car.

 

[creia]

The ignition fires every time the magnet passes the coil. The ignition runs off the crankshaft, not off the camsheft, like a distributor in a car.

I think you misunderstood my question. Why did you state that the tach should be set in the 2 cycle mode (and not the 4 cycle mode) when the OP has a 4 cycle engine?
Michael

 

[massacre]

I think you misunderstood my question. Why did you state that the tach should be set in the 2 cycle mode (and not the 4 cycle mode) when the OP has a 4 cycle engine?
Michael

Cam runs at 1/2 speed of crankshaft in a 4-stroke

 

[QuietVoyager]

I do not have a tach, are you able to send me a link for a good, cheap one? If not that’s ay-okay.

any cheap digital tach off amazon works fine, just wrap the wire around the spark plug wire